1. Field of the Invention
The present invention relates to the field of earth boring tools and in particular to core catchers used for retaining cores cut during coring operations.
2. Description of the Prior Art
Coring is a common practice in the field of pertroleum exploration, and it is not uncommon to encounter formations which are considered impossible to core because of their unconsolidated nature. For example, oil-sand, water-sand or loose debris constitute types of formations found in the field which extremely difficult to core.
Even if the loose, unconsolidated material can be successfully cored or cut, the problem still remains as to how to remove this material from the bore hole in a manner such that its original orientation is undisturbed. Alternatively, the problem may simply be how to remove the core at all. Typically, in prior art coring operations using conventional core catchers, such unconsolidated material will drop out of the core barrel as the core barrel is lifted to the surface of the hole.
What is needed then is some means whereby unconsolidated and loose material can be permitted to enter the core barrel but is prohibited from exiting, particularly when the barrel is lifted to the surface of the hole. Such a design should be able to operate successfully even when the formation is so soft and unconsolidated that the core must enter the barrel in an substantially unrestricted manner if its original orientation is to be preserved. In other words, what is needed is a coring system design that will not contact the core as it enters the barrel in any way, but will be able to completely retain the core when the barrel is lifted.